LONDON, Jan 12 (Reuters) - Workers at Britain’s Atomic Weapons Establishment (AWE), which provides and maintains the country’s nuclear warheads, will stage two 48-hour strikes in coming weeks in a dispute over their pensions, the Unite labour union said on Thursday.

AWE, which is jointly owned by U.S. firms Jacobs Engineering Group and Lockheed Martin and British support services group Serco, supports Trident, Britain’s submarine-based nuclear deterrent programme, under contract to the Ministry of Defence.

Unite said 600 of its members who are AWE employees at the two main facilities at Aldermaston and Burghfield in Berkshire, southeast England, would walk out for 48 hours, starting on Jan. 18 and on Jan. 30.

AWE has about 4,500 staff and 4,500 contractors in total working across all its sites.

“Unite members feel ‘deeply betrayed’ as promises made a quarter of a century ago guaranteeing their pensions, when they were transferred from the Ministry of Defence to the private sector, have been broken,” the union said in a statement.

AWE said in a statement it had offered staff a significantly improved scheme and additional enhanced benefits compared with the initial proposals.

It also said it had made contingency plans and had resilient measures in place to ensure staff and the general public remained safe during the strikes.

A spokesman for the Ministry of Defence (MoD) said it was being kept informed of developments.

“Safety and security of the AWE sites are of the highest priority and measures are in place to ensure these would not be compromised in the event of industrial action,” he said.

Unite said AWE management planned to close a defined benefit pension scheme on Jan. 31 and replace it with a defined contribution one in which final retirement income is not guaranteed.

“The most just course of action would be for the pension scheme to be taken back by the MoD,” said Unite regional officer Bob Middleton.

The MoD spokesman said changes to the AWE pension scheme were a matter for AWE to determine as the employer.

The union said 92 percent of its members at AWE, who include managers and manual workers, had voted for strike action. (Reporting by Estelle Shirbon; editing by Stephen Addison)